title: Antioxidant supplementation restores defective leucine stimulation of protein synthesis in skeletal muscle from old rats.
abstract: Aging is characterized by a progressive loss of muscle mass that could be partly explained by a defect in the anabolic effect of food intake. We previously reported that this defect resulted from a decrease in the protein synthesis response to leucine in muscles from old rats. Because aging is associated with changes in oxidative status, we hypothesized that reactive oxygen species-induced oxidative damage may be involved in the impairment of the anabolic effect of leucine with age. The present study assessed the effect of antioxidant supplementation on leucine-regulated protein metabolism in muscles from adult and old rats. Four groups of 8- and 20-mo-old male rats were supplemented or not for 7 wk with an antioxidant mixture containing rutin, vitamin E, vitamin A, zinc, and selenium. At the end of supplementation, muscle protein metabolism was examined in vitro using epitrochlearis muscles incubated with increasing leucine concentrations. In old rats, the ability of leucine to stimulate muscle protein synthesis was significantly decreased compared with adults. This defect was reversed when old rats were supplemented with antioxidants. It was not related to increased oxidative damage to 70-kDa ribosomal protein S6 kinase that is involved in amino acid signaling. These effects could be mediated through a reduction in the inflammatory state, which decreased with antioxidant supplementation. Antioxidant supplementation could benefit muscle protein metabolism during aging, but further studies are needed to determine the mechanism involved and to establish if it could be a useful nutritional tool to slow down sarcopenia with longer supplementation.
authors.affiliation: INRA, Centre de Clermont-Ferrand-Theix, UMR 1019, Unité Nutrition Humaine, Saint Genès Champanelle, F-63122 France.
authors.forename: Barbara
authors.initials: B
authors.lastname: Marzani
authors.forename: Michèle
authors.initials: M
authors.lastname: Balage
authors.forename: Annie
authors.initials: A
authors.lastname: Vénien
authors.forename: Thierry
authors.initials: T
authors.lastname: Astruc
authors.forename: Isabelle
authors.initials: I
authors.lastname: Papet
authors.forename: Dominique
authors.initials: D
authors.lastname: Dardevet
authors.forename: Laurent
authors.initials: L
authors.lastname: Mosoni
mesh_terms: D000375:Aging / Q000502:physiology*; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D015415:Biomarkers; D019587:Dietary Supplements; D007249:Inflammation / Q000378:metabolism; D007930:Leucine / Q000378:metabolism*; D009124:Muscle Proteins / Q000096:biosynthesis*; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000378:metabolism*; D018384:Oxidative Stress / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D019893:Ribosomal Protein S6 Kinases / Q000378:metabolism
chemical_list: D000975:Antioxidants; D015415:Biomarkers; D009124:Muscle Proteins; D019893:Ribosomal Protein S6 Kinases; D007930:Leucine